1. Field of the Invention
The present invention is directed to an electrode arrangement for an implantable defibrillator/cardioverter, the electrode arrangement being connected to the outputs of an implantable pulse generator, and the electrode arrangement being of the type having two intravascular electrodes, and a third, planar electrode disposed outside of the heart in the region of the left ventricle.
2. Related Application
The subject matter of the present application is related to that of application Ser. No. 07/595,859, filed simultaneously herewith, of the same inventors and assigned to the same Assignee as the present application.
3. Description of the Prior Art
An electrode arrangement as disclosed in U.S. Pat. No. 4,662,377, having two intravascular electrodes, one of which is disposed in the region of the superior vena cava, plus a third, planar electrode disposed outside of the heart in the region of the left ventricle. The two intravascular electrodes to be introduced into the right half of the heart are carried on a catheter spaced from each other so that one electrode comes to lie in the right ventricle of the heart and the other electrode comes to lie in the superior vena cava. The planar electrode, disposed opposite the left ventricle, is subcutaneously disposed outside of the heart. The planar electrode is connected to the electrode in the superior vena cava and to an output terminal of the pulse generator, which has another output terminal connected to the electrode in the ventricle. The catheter carries a cardiac pacing electrode at its distal end which, in combination with the electrode in the ventricle, serves to detect cardiac activity and to stimulate heart events.
As disclosed in U.S. Pat. No. 5,044,375, different respective catheters can be provided for the electrodes for defibrillating the heart and for the electrodes for detecting cardiac activity, however, care must be exercised when implanting catheters in the heart so that no short circuits between the defibrillation electrodes and the detector electrodes can arise.
Another electrode arrangement is disclosed in U.S. Pat. No. 4,708,145 for a defibrillator/cardioverter, wherein an electrode in the right ventricle and another electrode, positioned in the superior vena cava, are arranged on a common catheter, and a planar electrode is provided which can be disposed subcutaneously or epicardially or in the proximity of the diaphragm. Delivery of the defibrillation pulses ensues sequentially between the electrode in the superior vena cava and the electrode in the ventricle, and between the planar electrode and the electrode in the ventricle. The electrode disposed in the superior vena cava may alternatively be arranged in the inferior vena cava. An electrode arrangement is also disclosed in this patent wherein only planar electrodes are arranged on the heart.
Another electrode arrangement is disclosed in European Application 0 373 953 for defibrillating a heart wherein, when using three electrodes, one electrode is disposed in the right ventricle by means of a catheter, a further electrode is arranged in the vena cordis magna (great coronary vein) by means of a further catheter, and a third planar electrode is subcutaneously disposed opposite the left ventricle. Delivery of defibrillation energy can ensue between two or more of these electrodes, or alternatively sequential pulses can be delivered between individual pairs of electrodes.
The use of more than two electrodes when defibrillating the heart has the advantage of making possible a better distribution of the current density among different zones of the heart muscle. The aforementioned, known electrode arrangements having more than two electrodes all make use of an endocardial catheter carrying a ventricle electrode. Due to the size of the defibrillation electrodes, the increased demands made on the electrical insulation of the catheter results in thicker electrode leads being necessary in comparison to heart pacemaker leads. This means that endocardial catheters for defibrillation purposes will be relatively thick and stiff. This can result in undesirable mechanical irritation of the heart. The atrial-ventricular valves cannot close properly, and clots may increasingly form in the blood. It is conceivable, as known from the aforementioned U.S. Pat. No. 4,708,145, to provide only planar electrodes attached the heart (epicardially), however, such planar electrodes must be placed directly on the heart if the defibrillation energy is to be optimally exploited, which requires surgically opening the thorax to attach the electrodes.